Mushroom warhead

ABSTRACT

A warhead including a first section with a dish-shaped first fragmentation layer, and a second section with a barrel-shaped second fragmentation layer.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to fragmentation warheads and, moreparticularly, to a fragmentation warhead that achieves wide angularcoverage.

In attacking a ground target with a guided missile, it is desirable toget a reasonable dense coverage by the missile's explosive charge over abroad angle, relative to the missile axis, to take into account the factthat the target might not be a point target but might instead bedispersed around the aiming point, and also to take into account thefact that the actual point of impact could be displaced from the aimingpoint. FIG. 1 is a schematic axial cross section of the forward part ofa guided missile 10 with the prior art barrel-shaped fragmentationwarhead 12 of Zulkoski et al., U.S. Pat. No. 5,038,686, which patent isincorporated by reference for all purposes as if fully set forth herein.Guided missile 10 also includes, forward of warhead 12, a seeker head 14for guiding guided missile 10 to its target. FIG. 2 is a partialschematic axial cross section of warhead 12, showing that warhead 12consists of a central explosive charge 16 encased by a fragmentationlayer 18 and two bulkheads 20 and 22. Explosive charge 16 also has acylindrical recess 24 for a detonation fuse. Fragmentation layer 18 is abarrel-shaped layer of tungsten cubes held in a binder of pottingmaterial.

FIG. 3 shows the angular fragmentation pattern of warhead 12 whenwarhead 12 is detonated. This angular fragmentation pattern is theenvelope of the angular distribution of the trajectories of thefragments (the tungsten cubes in this case) of fragmentation layer 18when warhead 12 is detonated. The abscissa is azimuth, in degrees,laterally around guided missile 10 and warhead 12, and the ordinate ispolar angle, in degrees, relative to the cylindrical symmetry axes ofguided missile 10 and warhead 12, assuming that these axes arecoincident. A polar angle of zero degrees is straight forward relativeto guided missile 10. A polar angle of 180 degrees is straight aftrelative to guided missile 10. Warhead 12 achieves annular coverage.i.e. a full 360 degrees of azimuthal coverage but only partial (120degrees) polar angle coverage and no axial (straight forward or straightaft) coverage. In particular, a 60 degree solid angle forward of guidedmissile 10 is left uncovered. Continuing fragmentation layer 18 to coverthe forward part of warhead 14 in place of bulkhead 22 would provideforward coverage, except that the fragments emerging from warhead 12 inthe forward direction would lose kinetic energy while traversing seekerhead 14 and would emerge from guided missile 10 with insufficientkinetic energy to inflict damage on the target.

There is thus a widely recognized need for, and it would be highlyadvantageous to have, a fragmentation warhead, for a guided missile,that achieves uniform forward and lateral coverage.

SUMMARY OF THE INVENTION

According to the present invention there is provided a warheadincluding: (a) a first section including a substantially dish-shapedfirst fragmentation layer; and (b) a second section including asubstantially barrel-shaped second fragmentation layer.

According to the present invention there is provided a method ofdesigning a warhead to fit inside a space bounded by an envelope,including the steps of: (a) selecting a first radius of curvaturesufficient to provide a desired fragment density; (b) selecting a firstcenter of curvature within the space; (c) drawing a first circular arccentered on the first center of curvature and having the first radius ofcurvature until the first circular arc intersects the envelope; (d)drawing a straight line from the intersection of the first circular arcwith the envelope through the first center of curvature; (e) selecting asecond radius of curvature sufficient to provide the desired fragmentdensity; (f) selecting a second center of curvature; and (g) drawing asecond circular arc centered on the second center of curvature andhaving the second radius of curvature, the second circular arc startingfrom the straight line, the first circular arc and a portion of thestraight line between the first and second circular arcs defining afirst section of the warhead, the second circular arc defining a secondsection of the warhead.

The warhead of the present invention includes two sections, an aftsection similar to prior art warhead 12, and a forward section with asubstantially dish-shaped forward-facing fragmentation layer.Preferably, the forward-facing fragmentation layer is concave towardsthe second section.

FIGS. 4A and 4B are partial schematic axial cross sections of two basicembodiments 30A and 30B of the warhead of the present invention. Theforward section 32A of embodiment 30A includes a substantiallydish-shaped forward-facing fragmentation layer 36A and a forwardexplosive charge 40A. The aft section 34A of embodiment 30A isgeometrically similar to prior art warhead 12, and includes an aftfragmentation layer 38A and an aft explosive charge 42A. Fragmentationlayer 36A is concave towards aft section 34A. Similarly, the forwardsection 32B of embodiment 30B includes a substantially dish-shapedforward-facing fragmentation layer 36B and a forward explosive charge40B; the aft section 34B of embodiment 30B, which also is geometricallysimilar to prior art warhead 12, includes an aft fragmentation layer 38Band an aft explosive charge 42B; and fragmentation layer 36B is concavetowards aft section 34B. Having two separate fragmentation layersprovides fragmentation coverage in the forward direction as well aslaterally; but of the two embodiments, only embodiment 30B issufficiently long and heavy to generate fragments with a velocitysufficient to traverse seeker head 14 and exit with sufficient residualvelocity to inflict damage on the target.

Nevertheless, as discussed below, in preferred embodiments of thewarhead of the present invention, the two sections share a single commonexplosive charge that, when detonated, produces both a forwardfragmentation pattern corresponding to the forward-facing fragmentationlayer and an aft fragmentation pattern corresponding to the aftfragmentation layer. The common explosive charge includes a recess for afuse.

When the warhead of the present invention is detonated, the two sectionsproduce respective fragmentation patterns. Preferably, the twofragmentation patterns overlap and span a polar angle range of at least150 degrees. Preferably, the overlap is annular. Preferably, the firstsection produces a conical fragmentation pattern and the second sectionproduces an annular fragmentation pattern.

Fragmentation layers 36A and 36B both include central apertures.Alternatively, the forward-facing fragmentation sheet of the presentinvention is continuous.

The scope of the present invention also includes a guided missile thatincludes a warhead of the present invention. The warhead is aft of theguided missile's seeker head, and, of course, the aft section of thewarhead is aft of the forward section of the warhead. Preferably, thefirst section of the warhead spans the missile's fuselage.

The scope of the present invention also includes a method of designing awarhead that is to fit inside a confined space or envelope, such as thefuselage of a guided missile. To outline the forward section, a firstradius of curvature sufficient to provide a desired fragment density isselected, a first center of curvature is selected within the fuselage,and a first circular arc centered on the first center of curvature andhaving as its radius the first radius of curvature is drawn inside thefuselage until the first circular arc intersects the inner wall of thefuselage. A straight line is drawn through that intersection point andthrough the first center of curvature. To outline the aft section, asecond radius of curvature sufficient to provide the desired fragmentdensity is selected, a second center of curvature is selected within thefuselage, preferably on the straight line, and a second circular arccentered on the second center of curvature and having as its radius thesecond radius of curvature is drawn inside the fuselage. The portion ofthe first circular arc within the fuselage and the portion of thestraight line between the two circular arcs define the forward section.The second circular arc defines the aft section.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 is a schematic axial cross section of the forward part of aguided missile with a prior art warhead;

FIG. 2 is a partial schematic axial cross section of the warhead of FIG.1;

FIG. 3 shows the angular fragmentation pattern of the warhead of FIG. 1;

FIGS. 4A and 4B are partial schematic axial cross sections of two basicembodiments of a warhead of the present invention;

FIG. 5 is a schematic axial cross section of a preferred embodiment of awarhead of the present invention;

FIG. 6 shows the angular fragmentation pattern of the warhead of FIG. 5,

FIG. 7 shows plots of calculated fragment velocities for the warheads ofFIGS. 4A, 4B and 5;

FIG. 8 is a schematic axial cross section of the forward part of aguided missile with a warhead of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is of a fragmentation warhead which providessufficient kinetic energy to forward-emerging fragments to inflictdamage on a target after traversing components of a missile that arepositioned forward of the warhead.

The principles and operation of a fragmentation warhead according to thepresent invention may be better understood with reference to thedrawings and the accompanying description.

Returning now to the drawings, FIG. 5 is a schematic axial cross sectionof a preferred embodiment 50 of a warhead of the present invention. Asin embodiments 30A and 30B, the forward section 52 of embodiment 50includes a substantially dish-shaped forward-facing fragmentation layer56 and the aft section 54 of embodiment 50 includes a substantiallybarrel-shaped aft fragmentation layer 58. Forward-facing fragmentationlayer 56 is concave towards aft section 54. Note that to be within thescope of the present invention, the forward-facing fragmentation layerneeds to be only substantially dish-shaped: whereas forward-facingfragmentation layer 56 is truly dish-shaped, in the sense of beingcontinuous and without any holes or apertures, forward-facingfragmentation layers 36A and 36B both have central apertures where thebase of the dish would be. Fragmentation layers 56 and 58 arecylindrically symmetric and coaxial. Unlike embodiments 30A and 30B,embodiment 50 has a single explosive charge 60 that provides kineticenergy to the fragments of both fragmentation layers 56 and 58.Explosive charge 60 is provided with a cylindrical recess 62 for adetonation fuse.

FIG. 6 shows the angular fragmentation pattern of warhead 50 whenwarhead 50 is detonated. The fragmentation pattern 64 produced byforward section 52 is a conical pattern that spans an 80 degree solidangle in the forward direction. The fragmentation pattern 66 produced byaft section 54 is identical to the fragmentation pattern of prior artwarhead 12. Fragmentation patterns 64 and 66 have an annular overlapregion 68 between a polar angle of 30 degrees and a polar angle of 80degrees. The total polar angle span of the combined fragmentationpattern of warhead 50 as a whole is 150 degrees.

FIG. 7 shows plots of calculated fragment velocities for all threeembodiments of the warhead of the present invention. The “+” symbolsrefer to warhead 30A. The “*” symbols refer to warhead 30B. The circlesrefer to warhead 50. All three curves have two branches: a first branchthat spans a polar angle range from zero degrees to 80 degrees and whosefragments come from the forward-facing fragmentation layer, and a secondbranch that spans a polar angle range from 30 degrees to 150 degrees andwhose fragments come from the aft fragmentation layer. The fragmentsfrom all three aft fragmentation layers have similar velocities, asfunctions of polar angle. The fragments from forward-facingfragmentation layers 36B and 56 also have similar velocities, asfunctions of polar angles; and for polar angles less than 60 degrees,the velocities of fragments from forward-facing fragmentation layers 36Band 56 are significantly higher than the velocities of fragments fromforward-facing fragmentation layer 36A. The use of a common explosivecharge 60 for both fragmentation layers of warhead 50 enables warhead 50to have the same fragment velocity profile as warhead 30B while beingsignificantly shorter and lighter than warhead 30B. In particular, thereis synergy between the forward portion of explosive charge 60 in forwardsection 52 and the aft portion of explosive charge 60 in aft section 54in accelerating forward-facing fragmentation layer 56.

FIG. 8 is a schematic axial cross section of the forward part of aguided missile 80 of the present invention. Like prior art guidedmissile 10, guided missile 80 has seeker head 14 in its nose. Aft ofseeker head 14 is a warhead 70 of the present invention. Warhead 70includes a forward section 72 and an aft section 74. Aft of the nose ofguided missile 80, the fuselage 82 of guided missile 80 is a cylinderwith an axis 84 of cylindrical symmetry. Forward section 72 spansfuselage 82, as shown.

FIG. 8 also illustrates a method of designing a warhead of the presentinvention. A radius of curvature R₁ is selected for forward section 72that is sufficiently large to provide the desired fragment density. Acenter of curvature C₁ is selected within fuselage 82. A circular arc ofradius R₁ centered on point C₁ is constructed. The intersection of thecircular arc of radius R₁ with the inner wall of fuselage 82 defines themaximum transverse extent of forward section 72. A straight line L isdrawn from that intersection point through point C₁. A radius ofcurvature R₂ is selected for aft section 74 that is sufficiently largeto provide the desired fragment density. A center of curvature C₂ isselected on line L. A circular arc of radius R₂ centered on point C₂ isconstructed. Note that, in general, points C₁ and C₂ are not on axis 84.The circular arc of radius R₁ and the portion of line L between the twocircular arcs define forward section 72. The circular arc of radius R₂defines aft section 74. (More precisely, the surface of revolutionobtained by rotating the circular arc of radius R₁ and the portion ofline L between the two circular arcs about axis 84 defines forwardsection 72, and the surface of revolution obtained by rotating thecircular arc of radius R₂ about axis 84 defines aft section 74.)

If the circular arc of radius R₂ does not intersect fuselage 82 then thecircular arc of radius R₂ is continued until the desired fragmentationpattern polar angle range is obtained. If the circular arc of radius R₂intersects fuselage 82 then the process is repeated to design a thirdsection of the warhead.

While the invention has been described with respect to a limited numberof embodiments, it will be appreciated that many variations,modifications and other applications of the invention may be made.

1. A warhead comprising: (a) a first section including a substantiallydish-shaped first fragmentation layer; and (b) a second sectionincluding a substantially barrel-shaped second fragmentation layer. 2.The warhead of claim 1, wherein said first fragmentation layer isconcave towards said second section.
 3. The warhead of claim 1, whereinsaid first fragmentation layer is continuous.
 4. The warhead of claim 1,wherein said first fragmentation layer includes a central aperture. 5.The warhead of claim 1, further comprising; (c) a single explosivecharge that, when detonated, produces both a first fragmentation patterncorresponding to said first fragmentation layer and a secondfragmentation pattern corresponding to said second fragmentation layer.6. The warhead of claim 5, wherein said explosive charge includes arecess for a fuse.
 7. The warhead of claim 5, wherein said fragmentationpatterns overlap.
 8. The warhead of claim 7, wherein said firstfragmentation pattern is conical and wherein said second fragmentationpattern is annular.
 9. The warhead of claim 7, wherein said overlap isannular.
 10. The warhead of claim 7, wherein said fragmentation patternsspan a polar angle range of at least about 150 degrees.
 11. The warheadof claim 5, wherein said first fragmentation pattern is conical andwherein said second fragmentation pattern is annular.
 12. The warhead ofclaim 1, wherein, when the warhead is detonated, said sections produceoverlapping respective fragmentation patterns.
 13. The warhead of claim12, wherein said fragmentation patterns span a polar angle range of atleast about 150 degrees.
 14. The warhead of claim 12, wherein saidoverlap is annular.
 15. The warhead of claim 1, wherein, when thewarhead is detonated, said first section produces a conicalfragmentation pattern and said second section produces an annularfragmentation pattern.
 16. A missile comprising the warhead of claim 1.17. The missile of claim 16, further comprising a fuselage, and whereinsaid first section substantially spans said fuselage.
 18. The missile ofclaim 16, wherein said second section is aft of said first section. 19.The missile of claim 16, further comprising a seeker head, the warheadbeing aft of said seeker head.
 20. A method of designing a warhead tofit inside a space bounded by an envelope, comprising the steps of: (a)selecting a first radius of curvature sufficient to provide a desiredfragment density; (b) selecting a first center of curvature within thespace; (c) drawing a first circular arc centered on said first center ofcurvature and having said first radius of curvature until said firstcircular arc intersects said envelope; (d) drawing a straight line fromsaid intersection of said first circular arc with said envelope throughsaid first center of curvature; (e) selecting a second radius ofcurvature sufficient to provide said desired fragment density; (f)selecting a second center of curvature; and (g) drawing a secondcircular arc centered on said second center of curvature and having saidsecond radius of curvature, said second circular arc starting from saidstraight line, said first circular arc and a portion of said straightline between said first and second circular arcs defining a firstsection of the warhead, said second circular arc defining a secondsection of the warhead.
 21. The method of claim 20, wherein said secondcenter of curvature is on said straight line.